The numerous processes of biological systems, from development to homeostasis, argue for mechanisms of metabolic control. The understanding of these mechanisms is of paramount importance in comprehending normal and abnormal cellular growth and differentiation. With this in mind, we wish to continue our studies on the mechanism of multivalent repression and the possible role of tRNA in this process. In multivalent repression, regulation is accomplished by the intervention of a variety of small and large molecules. This system, therefore, provides a model to study a regulatory process involved in the control of protein synthesis that receives and responds to signals from a number of cellular constituents. Since multivalent repression is found in pathways of biosynthesis it may provide a general mechanism for development and differentiation. We plan to probe the role of aminoacyl-tRNA synthetases, tRNA and allosteric biosynthetic enzymes, to understand the molecular bases for multivalent repression.